Abstracts

Change in body weight is a common consequence of therapy with certain antiepileptic drugs. Weight gain is one of the most commonly reported adverse effects of therapy with valproic acid (VPA) occurring in about 50% of VPA-treated patients. Increases in body weight associated with VPA treatment pose considerable, well-documented health risks such as insulin resistance, hypertension, diabetes mellitus, and coronary artery disease which might be especially relevant in elderly patients. So far it was said that there are no predictive factors for weight gain such as age, gender, pretreatment body weight, or valproate dosage. But in most studies the mean age of investigated patients was in the younger age group. We studied all patients newly treated with VPA for the diagnosis of epilepsy in the time period between May 2000 and May 2003 at the Department of Neurology, Kantonsspital St. Gallen, Switzerland. Investigated parameters included age, gender, body weight, and body mass index (BMI) at beginning of therapy and at the end of therapy or in August 2003, respectively. Included were 23 consecutive patients, 22 of them on VPA monotherapy, one patient with add-on CBZ and LTG. There were 15 women and 8 men with a mean age of 61.7 years ranging from 35 to 81 years. Mean body weight was 67.0 kg (range 45-88 kg) and mean BMI 24.4 (range 18-37) at beginning of therapy. After a mean observational period of 10.5 months the mean body weight was 67.4 kg and the mean BMI 24.5, respectively. Only 4 patients gained weight with an increase of BMI between 1 and 4.
All these 4 patients including 3 women and one man were younger than 55 years (mean age 49 years, range 45-52). In the overall study group there were only 9 patients with increase of body weight within the age group [lt]55 years. In contrast, none of the patients aged 55 or above had a weight gain, 6 patients in this age group even lost some weight.
Considering age effects, the mean BMI before therapy was 25.3 for patients [lt]55 years of age and 23.9 for patients [ge]55 years. On VPA therapy these values were 26.1 and 23.6, respectively. Contrary to previously reported side effects of VPA with an incidence of weight gain in about 50% of patients we did not find any increase of body weight in patients newly treated with with VPA at age 55 or aboveSo far, only Isojarvi (Ann Neurol 1996;39:579-584) reported a slightly lower percentage of women above age 20 with weight gain on VPA as compared to the younger age group.The metabolic causes of valproate-induced weight gain remain still unclear. Several mechanisms have been postulated including increased appetite and food intake, decreased beta oxidation of fatty acids, and hyperinsulinemia. Previously no predictive factor for weight gain was desribed. Considering our results age is a predictive factor for weight gain with no increase of body weight in elderly patients newly treated with VPA. This is of major importance considering the negative impact of weight gain on general health.